Lyme disease is the most common vector borne disease in the United States. Although antibiotic therapy is clinically effective in treating the symptoms of Lyme disease for patients early in the course of disease, a significant number of patients who receive delayed therapy report persistent symptoms. The cause of persistent symptoms in patients after antibiotic therapy for Lyme disease remains highly controversial. Theories include persistence of infection, induction of autoimmune responses and non-healing tissue damage. There is currently no good test to document resolution of infection and clearance of the organism, Borrelia burgdorferi. Although the prevailing belief in the scientific community has been that bacteria are completely cleared after antibiotic therapy, recent studies in mice and dogs have shown that bacteria can persist after treatment and are detectable by PCR or xenodiagnosis (the feeding of uninfected Ixodes ticks on the treated animals). Xenodiagnosis has been used for other difficult to diagnose diseases such as Chagas disease. Organisms may be specifically adapted to their natural vector and xenodiagnosis can sometimes definitively identify the presence of an organism where other techniques cannot. Here in this pilot proposal, we will test the utility of xenodiagnosis for identifying persistence of B. burgdorferi in treated human Lyme disease. In specific aim #1, we will test subjects who have the characteristic erythema migrans (EM) rash and have been treated with antibiotics early in the course of Lyme disease. Although these patients generally do well after antibiotic therapy, at least one other study has shown that B. burgdorferi DNA continues to be present in the EM site after treatment and animal studies show the highest recovery of the organism during these early time points. We will perform biopsies of the EM site after completion of antibiotics and then allow 25-30 larval Ixodes ticks to feed on the subject. Repleted ticks will be collected, allowed to molt to their nymphal stage and then fed on severe combined immunodeficiency (SCID) mice. The repleted nymphal ticks and the SCID mice will be tested for the presence of B. burgdorferi by PCR and culture. Evidence of acquisition of bacteria by xenodiagnostic ticks in specific aim #1 would provide proof of principle that B. burgdorferi are able to persist after antibiotic therapy. In Specific Aim #2, we will perform similar studies, but enrollment will target subjects with persistent symptoms after antibiotic therapy. Evidence that B. burgdorferi can be recovered by xenodiagnosis after antibiotic therapy in subjects with continued symptoms would change the current paradigm for potential mechanisms of disease and provide researchers and clinicians a tool for identifying patients with persistent infection PUBLIC HEALTH RELEVANCE: The cause of persistent symptoms after antibiotic therapy for Lyme disease is an area of great controversy. Recent studies have shown that the organism may persist in animals after antibiotic therapy and can be detected by using the natural tick vector to acquire the organism through feeding (xenodiagnosis). Whether this occurs in humans is unknown; in this study, we seek to determine whether xenodiagnosis can detect B. burgdorferi in humans after antibiotic therapy.